Altcoin Season Index

The Altcoin Season Index, maintained by CoinMarketCap and Blockchaincenter.net, provides a simple quantitative measure of altcoin market performance relative to Bitcoin. The calculation: if 75% or more of the top 50 altcoins outperformed Bitcoin over the last 90 days, the index is in "altcoin season." If 25% or fewer outperformed Bitcoin, it's "Bitcoin season."

This metric captures the rotation that occurs within crypto market cycles. During early and mid bull markets, Bitcoin typically leads. As Bitcoin's gains slow and the cycle matures, capital rotates into Ethereum, then large-cap altcoins, then mid and small caps — each wave amplifying both gains and eventual losses. The full altcoin season rotation (all 50 top altcoins beating Bitcoin) historically occurs in the final 3-6 months before a major cycle top.

Understanding the altcoin season cycle helps with allocation timing. During Bitcoin-dominant phases (index below 25), most altcoins underperform and adding altcoin exposure typically underperforms simply holding more Bitcoin. As the index climbs above 50 and approaches 75, the risk/reward for selective altcoin exposure improves. Once the index exceeds 90, historical data suggests it's often late in the cycle — very high altcoin valuations tend to correct sharply when Bitcoin's momentum fades. The Alpha Factory Altcoin Rules incorporates BTC dominance and relative performance metrics, which directly relate to the altcoin season index.